WM8983
Product Preview
OUTPUT SIGNAL PATH
The WM8983 output signal paths consist of digital application filters, up-sampling filters, stereo Hi-Fi
DACs, analogue mixers, stereo headphone and stereo line/mono/midrail output drivers. The digital
filters and DAC are enabled by register bits DACENL And DACENR. The mixers and output drivers
can be separately enabled by individual control bits (see Analogue Outputs). Thus it is possible to
utilise the analogue mixing and amplification provided by the WM8983, irrespective of whether the
DACs are running or not.
The WM8983 DACs receive digital input data on the DACDAT pin. The digital filter block processes
the data to provide the following functions:
•
•
•
•
Digital volume control
Graphic equaliser
A digital peak limiter.
Sigma-Delta Modulation
High performance sigma-delta audio DAC converts the digital data into an analogue signal.
Figure 21 DAC Digital Filter Path
The analogue outputs from the DACs can then be mixed with the aux analogue inputs and the ADC
analogue inputs. The mix is fed to the output drivers for headphone (LOUT1/ROUT1,
LOUT2/ROUT2) or line (OUT3/OUT4). OUT3 and OUT4 have additional mixers which allow them to
output different signals to the headphone and line outputs.
DIGITAL PLAYBACK (DAC) PATH
Digital data is passed to the WM8983 via the flexible audio interface and is then passed through a
variety of advanced digital filters as shown in Figure 21 to the hi-fi DACs. The DACs are enabled by
the DACENL/R register bits.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R3
0
DACENL
0
Left channel DAC enable
0 = DAC disabled
Power
Management 3
1 = DAC enabled
1
DACENR
0
Right channel DAC enable
0 = DAC disabled
1 = DAC enabled
Table 19 DAC Enable Control
The WM8983 also has a Soft Mute function, which when enabled, gradually attenuates the volume
of the digital signal to zero. When disabled, the gain will ramp back up to the digital gain setting. This
function is enabled by default. To play back an audio signal, it must first be disabled by setting the
SOFTMUTE bit to zero.
PP Rev 1.1 August 2005
38
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
